Magnets as Brakes?

Now magnets are everywhere, they're in computers televisions hi-fi's fans washing machines stereo equipment tape players, absolutely everywhere, right down to the humble fridge magnet and they vary in scale enormously from the microscopic right up to the planetary. That's right folks we're sitting on the biggest magnet of all, the earth itself.

So what is a magnet? Well a magnet is defined as any object that attracts iron and produces an external magnetic field, and as you probably learnt at school the region at the end of the magnet where external magnetic fields are strongest are called the poles.

NARRATOR:

And every magnet has two, one north and one south, and the first law of magnetism is that opposite poles attract while the same poles repel.

RICHARD AMBROSE:

And because the earth is one big magnet if you suspend a simple bar magnet within the earth's magnetic field, it will naturally orientate itself north to south and this is exactly how a compass works.

RICHARD AMBROSE:

It's been discovered that homing pigeons have got a naturally occurring magnetic mineral in their beaks called magnetite; this makes them sensitive to the earth's magnetic field and helps with their navigation.

One of the most surprising things about magnetism is its relationship to electricity. Did you know for example, you can generate an electric current using a magnet? Now underneath this tape is copper wire wrapped around this copper tube, if I drop a magnet through the tube, it generates an electric current in the wire which will light up these LED's.

NARRATOR:

This process is called electromagnetic conduction.

And perhaps one of the most surprising applications of electromagnetic conduction can be found on the powerful breaks used on some fairground rides.

RICHARD AMBROSE:

The break system of the awesome theme park ride is totally reliant on magnets.

JONNY PHILLIPS:

Come on Rich lets get it over with.

RICHARD AMBROSE:

All right.

NARRATOR:

This ride is brilliant in its simplicity. The two ton cars are winched to the top of the 60 meter tower by powerful electric motors.

RICHARD AMBROSE:

Right come on we can do it.

NARRATOR:

And boy is it a long way up.

RICHARD AMBROSE:

Oh no oh no. Oh no. No. No.

JONNY PHILLIPS:

Ready, look at me, look at me, look at me.

(both screaming)

NARRATOR:

Like all magnets, the magnets in the drop car produce their own magnetic field, they're shown here in red, as the car falls at 22 meters per second it passes these copper fins and the falling motion across these fins creates an electric current, which in turn creates its own magnetic field.

However, this field is equal and opposite to the fields created by the magnets in the drop car, the effect of these opposing magnetic fields is so powerful it brings the car to a halt. It's called edicurrent breaking and it's amazing.